Alarm Section; Nibp Pump Control; Safety Devices - Mallinckrodt NELLCOR NPB-4000 Service Manual

Section 15: Drawings

15.10 ALARM SECTION

15.10.1 Alarm Control
15.10.2 Alarm Sounder

15.11 NIBP PUMP CONTROL

15.12 SAFETY DEVICES

15-10
When the supply is first turned on, R82 tries to charge C54. During the 300-500
milliseconds charge-up time, it is expected that the supply will come into
operation, and the processor board will return sync pulses. The sync pulse will
drive Q20 to discharge C54. If the sync pulses stop for any reason, C54 will rise,
which will activate the alarm sounder and shut off the supply .
Flip flop U9 latches an alarm condition and is also used to stop a sounding
alarm. The flip flop is reset by PWRRST, or by a push of the front panel
SILENCE push button.
A SET condition of U9 will turn on FETs Q21 and Q22. With power applied,
timing U13 will oscillate and drive the speaker lead with the alarm waveform.
The power supply mechanical assembly holds the blood pressure pump and
shield. The power supply contains circuitry that allows logic level control of the
pump power from the processor board. For single point fault protection, the
pump requires two signals (PUMPON and PVENB) to activate the pump. The
PUMPON signal (when high) turns on the N-channel FET section of U15, which
pulls the bottom lead of the motor to ground. The PVENB signal, through level
translator Q19, turns on the P channel section of U15, which pulls the top motor
lead to VBATT.
Diode D32, capacitor C46, and resistor R77 provide noise control during motor
operation.
A number of safety devices serve to limit the severity of fault-induced problems.
• Fuse-Limited AC high input lead
• Fuse-Limited AC Low input lead
• Fuse-Limited external DC input lead
• Fuse-Limited VBATT lead for system supply operation
• Polyswitch
®
(self-resetting fuse) protected VBATSNS lead for control
logic and Main Board usage
• Two signals and two paths required to activate the NIBP pump
• Short-circuit protected AC Mains Supply
• Short-circuit protected charger
• Short-circuit protected system supply (current-limiting and three
polyswitches)
• Alarm sound if processor fails